limiter.acquire(Integer.MAX_VALUE / 4);
    limiter.acquire(Integer.MAX_VALUE / 2);
    limiter.acquire(Integer.MAX_VALUE);
    assertEvents("R0.00", "R0.00", "R0.00"); // no wait, infinite rate!

    limiter.setRate(2.0);
    limiter.acquire();
    limiter.acquire();
    limiter.acquire();
    limiter.acquire();
    limiter.acquire();
    assertEvents(

    limiter.acquire(Integer.MAX_VALUE / 4);
    limiter.acquire(Integer.MAX_VALUE / 2);
    limiter.acquire(Integer.MAX_VALUE);
    assertEvents("R0.00", "R0.00", "R0.00"); // no wait, infinite rate!

    limiter.setRate(2.0);
    limiter.acquire();
    limiter.acquire();
    limiter.acquire();
    limiter.acquire();
    limiter.acquire();
    assertEvents(

   */
  @CanIgnoreReturnValue
  public double acquire() {
    return acquire(1);
  }

  /**
   * Acquires the given number of permits from this {@code RateLimiter}, blocking until the request
   * can be granted. Tells the amount of time slept, if any.
   *
   * @param permits the number of permits to acquire
   * @return time spent sleeping to enforce rate, in seconds; 0.0 if not rate-limited

 *
 * <p>Deadlocks can arise when locks are acquired in an order that forms a cycle. In a simple
 * example involving two locks and two threads, deadlock occurs when one thread acquires Lock A, and
 * then Lock B, while another thread acquires Lock B, and then Lock A:
 *
 * <pre>
 * Thread1: acquire(LockA) --X acquire(LockB)
 * Thread2: acquire(LockB) --X acquire(LockA)
 * </pre>
 *

     * <p>To avoid races between threads doing release and acquire, we transition to the final state
     * in two steps. One thread will successfully CAS from RUNNING to COMPLETING, that thread will
     * then set the result of the computation, and only then transition to COMPLETED, CANCELLED, or
     * INTERRUPTED.
     *
     * <p>We don't use the integer argument passed between acquire methods so we pass around a -1
     * everywhere.
     */

     * <p>To avoid races between threads doing release and acquire, we transition to the final state
     * in two steps. One thread will successfully CAS from RUNNING to COMPLETING, that thread will
     * then set the result of the computation, and only then transition to COMPLETED, CANCELLED, or
     * INTERRUPTED.
     *
     * <p>We don't use the integer argument passed between acquire methods so we pass around a -1
     * everywhere.
     */

    // Put a floor on the keep alive duration, otherwise cleanup will spin loop.
    require(keepAliveDuration > 0L) { "keepAliveDuration <= 0: $keepAliveDuration" }
  }

  fun idleConnectionCount(): Int =
    connections.count {
      it.withLock { it.calls.isEmpty() }
    }

  fun connectionCount(): Int = connections.size

  /**
   * Attempts to acquire a recycled connection to [address] for [call]. Returns the connection if it

* Nginx
* HAProxy

## Let's Encrypt { #lets-encrypt }

Before Let's Encrypt, these **HTTPS certificates** were sold by trusted third parties.

The process to acquire one of these certificates used to be cumbersome, require quite some paperwork and the certificates were quite expensive.

But then **[Let's Encrypt](https://letsencrypt.org/)** was created.

    //                                                                    ================

    /**
     * Attempts to acquire a distributed lock for the specified operation.
     *
     * @param operationName the operation name used as the lock document ID.
     * @return {@code true} if the lock was acquired.
     */
    public boolean tryStartOperation(final String operationName) {
        return tryStartOperation(operationName, null);

///

### `startup` and `shutdown` together { #startup-and-shutdown-together }

There's a high chance that the logic for your *startup* and *shutdown* is connected, you might want to start something and then finish it, acquire a resource and then release it, etc.

Doing that in separated functions that don't share logic or variables together is more difficult as you would need to store values in global variables or similar tricks.